Biometric-Sensor Assembly, Such as for Acoustic Reflectometry of the Vocal Tract

ABSTRACT

A biometric-sensor assembly, e.g., for acoustic reflectometry of the vocal tract. In one embodiment, the sensor assembly includes a dental appliance for in-mouth mounting, an acoustic sensor attached to the dental appliance, and an optional headset. The dental appliance enables secure placement of the acoustic sensor in the mouth of the user, e.g., for tracking movements of the tongue and/or other internal articulators of the vocal tract. A boom arm of the headset can be used for holding an additional acoustic sensor and/or a miniature video camera, e.g., for tracking movements of the lips.

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject matter of the present application is related to the subjectmatter of (1) U.S. Patent Application Publication No. 2010/0131268, (2)U.S. patent application Ser. No. 12/956,552, filed Nov. 30, 2010, andentitled “Voice-Estimation Based on Real-Time Probing of the VocalTract,” and (3) U.S. patent application Ser. No. 13/076,652, filed Mar.31, 2011, and entitled “Passband Reflectometer,” all of which areincorporated herein by reference in their entirety.

The subject matter of this application is also related to the subjectmatter of U.S. patent application Ser. No. ______, by Lothar Moeller,attorney docket reference 809412-US-NP, filed on the same date as thepresent application, and entitled “HUMAN/MACHINE INTERFACE FOR USING THEGEOMETRIC DEGREES OF FREEDOM OF THE VOCAL TRACT AS AN INPUT SIGNAL,”which is incorporated herein by reference in its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to human-machine interfaces and, morespecifically but not exclusively, to biometric sensors for probing thegeometric shape of the vocal tract.

2. Description of the Related Art

This section introduces aspects that may help facilitate a betterunderstanding of the invention(s). Accordingly, the statements of thissection are to be read in this light and are not to be understood asadmissions about what is in the prior art or what is not in the priorart.

The use of various biological signals produced by the human body forcontrolling machines and/or devices is currently being actively pursued.Body signals other than limb motion are useful, for example, for peoplewith disabilities or when the hands/legs are being used for otherfunctions. However, a human/machine interface suitable for thesepurposes and its various components, such as biometric sensors, are notyet sufficiently developed.

SUMMARY

Disclosed herein are various embodiments of a biometric-sensor assembly,e.g., for acoustic reflectometry of the vocal tract. In one embodiment,the sensor assembly includes a dental appliance for in-mouth mounting,an acoustic sensor attached to the dental appliance, and an optionalheadset. The dental appliance enables secure placement of the acousticsensor in the mouth of the user, e.g., for tracking movements of thetongue and/or other internal articulators of the vocal tract. A boom armof the headset can be used for holding an additional acoustic sensorand/or a miniature video camera, e.g., for tracking movements of thelips.

According to one embodiment, provided is an apparatus having a firstacoustic speaker, a first set of one or more acoustic microphones, and adental appliance. The first acoustic speaker and the first set of one ormore acoustic microphones are attached to the dental appliance. When thedental appliance is placed into a user's mouth, the first acousticspeaker has a position that causes acoustic waves generated by the firstacoustic speaker to enter the user's vocal tract, and the first set ofone or more acoustic microphones has a position that causes acousticwaves reflected from the vocal tract to impinge onto at least onemicrophone of the first set.

According to another embodiment, provided is an apparatus having anacoustic speaker, a set of one or more acoustic microphones, and aheadset having an earpiece and a boom arm that is movable with respectto the earpiece. The acoustic speaker is mounted on the boom arm. Theset of one or more acoustic microphones is also mounted on the boom arm.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, features, and benefits of various embodiments of theinvention will become more fully apparent, by way of example, from thefollowing detailed description and the accompanying drawings, in which:

FIG. 1 shows a block diagram of a system having a human/machine (HM)interface according to one embodiment of the invention;

FIGS. 2A-2B show front and back views, respectively, of a sensorassembly that can be used in the HM interface of the system shown inFIG. 1 according to one embodiment of the invention;

FIG. 3 shows a perspective three-dimensional view of a sensor assemblythat can be used in the HM interface of the system shown in FIG. 1according to another embodiment of the invention;

FIG. 4 shows a perspective three-dimensional view of a sensor assemblythat can be used in the HM interface of the system shown in FIG. 1according to yet another embodiment of the invention; and

FIGS. 5A-5B show perspective three-dimensional views of a headset andits certain components that can be used in the HM interface of thesystem shown in FIG. 1 according to yet another embodiment of theinvention.

DETAILED DESCRIPTION

FIG. 1 shows a block diagram of an operator-controlled system 100according to one embodiment of the invention. System 100 has ahuman/machine (HM) interface 110 that enables an operator (user) 102 tocontrol the operation of a machine 150 using nonverbal signals producedby his/her vocal tract 104 and/or geometric degrees of freedom (DOFs) ofthe vocal tract. In various embodiments, machine 150 may be, withoutlimitation, a mobility and/or prosthetic system for a disabledindividual, a vehicle-control system, a multi-media system, acommunication device, a machine that is being operated in a hostileenvironment (such as underwater, outer space, under high g-forces, orfire), and a weapon-control system.

Vocal tract 104 has multiple DOFs that enable intelligible speech andadditional DOFs that are not used for speaking. For example, cartilagestructures of the larynx can rotate and tilt variously to change theconfiguration of the vocal folds. When the vocal folds are open,breathing is permitted. The opening between the vocal folds is known asthe glottis. When the vocal folds are closed, they form a barrierbetween the laryngopharynx and the trachea. When the air pressure belowthe closed vocal folds (i.e., sub-glottal pressure) is sufficientlyhigh, the vocal folds are forced open. As the air begins to flow throughthe glottis, the sub-glottal pressure drops and both elastic andaerodynamic forces return the vocal folds into the closed state. Afterthe vocal folds close, the sub-glottal pressure builds up again, therebyforcing the vocal folds to reopen and pass air through the glottis.Consequently, the sub-glottal pressure drops, thereby causing the vocalfolds to close again. This periodic process (known as phonation)produces a sound corresponding to the configuration of the vocal foldsand can continue for as along as the lungs can build up sufficientsub-glottal pressure. In general, the vocal folds will not oscillate ifthe pressure differential across the larynx is not sufficiently large.

The sound produced by the vocal folds is modified as it passes throughthe upper portion of vocal tract 104. More specifically, variouschambers of vocal tract 104 act as acoustic filters and/or resonatorsthat modify the sound produced by the vocal folds. The followingprincipal chambers of vocal tract 104 are usually recognized: (i) thepharyngeal cavity located between the esophagus and the epiglottis; (ii)the oral cavity defined by the tongue, teeth, palate, velum, and uvula;(iii) the labial cavity located between the teeth and lips; and (iv) thenasal cavity. The shapes of these cavities can be changed by moving thevarious articulators of vocal tract 104, such as the velum, tongue,lips, jaws, etc. No sound is produced when a person simply moves thetongue, lips, and/or the lower jaw.

While operating system 100, operator 102 can activate the various partsof vocal tract 104 without producing a sound. For example, operator 102can change the geometry of vocal tract 104 by consciously moving thetongue, lips, and/or jaws, without forcing an air stream through thelarynx. Alternatively, operator 102 can change the geometry of vocaltract 104 by going through a mental act of “speaking to oneself,” whichcauses the brain to send appropriate signals to the muscles that controlthe various articulators in the vocal tract without causing the vocalfolds to oscillate. HM interface 110 characterizes the geometric shapeof vocal tract 104 and/or its changes, e.g., as further described below,and then interprets the characterization results to generate acorresponding control signal (e.g., instruction or command) 138. Invarious embodiments, control signal 138 can be an analog signal or adigital signal. In one embodiment, operator 102 has control over thetype of control signal 102 and can switch it between the analog anddigital modes as appropriate or necessary. The latter feature mayadvantageously enable operator 102 to control machine 150 in a varietyof fast-changing situations, for example, those experienced by a jetpilot under high-g forces.

Based on control signal 138, controller 140 configures machine 150 toperform a corresponding appropriate operation and/or function. Invarious embodiments, HM interface 110 can generate control signal 138 ina manner that enables (i) a continuous change of an operating parameterfor machine 150 and/or (ii) a discrete change in the operatingconfiguration or state of that machine. Representative examples ofcontinuous changes include, without limitation, (a) changing the speedand/or direction of motion, (b) moving a robotic arm or tool, (c) movinga cursor across a display screen, (d) tuning a radio, and (e) adjustingthe brightness and/or contrast of an image generated by night-visiongoggles. Representative examples of discrete changes include, withoutlimitation, (a) selecting an item or pressing an emulated button on adisplay screen, (b) starting or stopping an engine, (c) sending a silentmessage, and (d) firing a weapon.

In various embodiments, HM interface 110 can have different sensorsconfigured to generate signals that characterize the geometricconfiguration of vocal tract 104. In the embodiment shown in FIG. 1, HMinterface 110 includes a video camera 120 and an acoustic sensorcomprising a speaker 116 and a microphone 118. In alternativeembodiments, other suitable sensors and/or additional speakers andmicrophones (not explicitly shown in FIG. 1) may similarly be used. In arepresentative embodiment, HM interface 110 has at least one speaker andat least one microphone.

HM interface 110 has mechanical means (not explicitly shown in FIG. 1)for positioning and/or fixing the position of speaker 116, microphone118, and camera 120 near the entrance to vocal tract 104, e.g., in oroutside the mouth of operator 102 (also see FIGS. 2-5). Speaker 116operates under the control of a controller 112 and is configured to emitshort (e.g., shorter than about 1 ms) bursts of acoustic waves forprobing the shape of vocal tract 104. In a representative configuration,a burst of acoustic waves generated by speaker 116 undergoes multiplereflections within the various cavities of vocal tract 104. Thereflected acoustic waves are detected by microphone 118, and theresulting electrical signal is converted into digital form and appliedto a digital signal processor 124 for processing and analyses. Adigital-to-analog (D/A) converter 114 provides an interface between (i)controller 112, which operates in the digital domain, and (ii) speaker116, which operates in the analog domain. An analog-to-digital (A/D)converter 122 provides an interface between (i) microphone 118, whichoperates in the analog domain, and (ii) processor 124, which operates inthe digital domain. Controller 112 and processor 124 may use adigital-signal bus 126 to aid one another in the generation of drivesignals for speaker 116 and the deconvolution of the response (echo)signals detected by microphone 118. Processor 124 uses the signalsdetected by microphone 118 together with the images captured by camera120 to characterize the geometric configuration of vocal tract 104 andgenerate control signal 138 for controller 140.

As used herein, the term “acoustic” encompasses (i) sound waves from thehuman audio-frequency range (e.g., between about 15 Hz and about 20 kHz)and (ii) ultrasound waves (i.e., quasi-audio waves whose frequency ishigher than the upper boundary of the human audio-frequency range, e.g.,higher than about 20 kHz). Additional sensors for HM interface 110 canoptionally be selected from a set consisting of an infrared sensor orimager, a millimeter-wave sensor, an electromyographic sensor, and anelectromagnetic articulographic sensor. Further description of possibleuses of these additional sensors can be found, e.g., in the above-citedU.S. Patent Application Publication No. 2010/0131268.

In one configuration, HM interface 110 characterizes the geometric shapeof vocal tract 104 by repeatedly measuring its reflected impulseresponse. As used herein, the term “impulse response” refers to an echosignal produced by vocal tract 104 in response to a single, very shortexcitation impulse. Mathematically, an ideal excitation impulse thatproduces an ideal impulse response is described by the Dirac deltafunction for continuous-time systems or by the Kronecker delta fordiscrete-time systems. Since the excitation waveforms that are generatedin practice are not ideal, the impulse response measured by HM interface110 is an approximation of the ideal impulse response. In particular,various components of HM interface 110 may band-limit the frequencyspectrum of the excitation pulse(s), limit the amplitude of theexcitation pulses (e.g., to avoid undesired nonlinear effects), and/orband-limit the frequency spectrum of the detected reflected waves. Theterm “impulse response” should be construed to encompass both thetransmitted impulse response and the reflected impulse response. In thecontext of HM interface 110, the measured impulse response is areflected impulse response. However, known algorithms can be used toconvert the measured reflected impulse response into a correspondingtransmitted impulse response, with the latter being the impulse responsethat would have been measured at the distal end of vocal tract 104,e.g., the glottis.

When operator 102 changes the geometric shape of vocal tract 104, e.g.,by moving the tongue, the impulse response of the vocal tract changes.In a representative configuration, HM interface 110 captures thecorresponding series of impulse responses in real time, e.g., asdescribed in the above-referenced U.S. patent application Ser. No.13/076,652. Processor 124 can then use different signal-processingtechniques to translate the captured impulse responses into controlsignal 138.

For example, in one embodiment, the signal processing implemented inprocessor 110 includes the determination, in some approximation, of theactual geometric shapes adopted by vocal tract 104, e.g., as describedin the above-referenced U.S. patent application Ser. No. 12/956,552. Theuse of two or more microphones 118 configured for spatially resolveddetection of impulse-responses enables HM interface 110 to recognizedifferent asymmetrical shapes of vocal tract 104, with the asymmetrybeing ascertained with respect to the natural (left/right) plane ofsymmetry of the vocal tract. For example, acoustic signals detected bytwo or more microphones 118 placed at different laterally offsetpositions enable HM interface 110 to distinguish between a vocal-tractgeometry in which the tongue is shifted toward the left cheek and theminor-image geometry in which the tongue is equally shifted toward theright cheek.

In various embodiments, the signal processing implemented in processor110 may be based on signal-feature selection and/or signal-featurequantification. A representative, non-exclusive list of signal featuresthat can be selected for analysis includes (i) the delay between theexcitation pulse and the corresponding impulse response, (ii) theamplitude and/or phase of a particular impulse response, (iii) theamplitude and/or phase of a differential impulse response derived fromtwo impulse responses detected by two different microphones 118, and(iv) a frequency spectrum of an impulse response. In a representativeembodiment, signal-feature quantification includes quantification of oneor more parameters that describe the selected signal feature. Arepresentative, non-exclusive list of possible signal-featurequantification steps includes (i) comparing a delay time with one ormore reference values, (ii) comparing the intensity of a selectedspectral component with one or more reference values, (iii) measuringthe frequency of a characteristic frequency component of a signal, (iv)comparing a list of frequency components of a signal with a referencelist, (v) comparing the intensities of two or more different frequencycomponents with one another, (v) determining an amplitude and/or phasecorresponding to a differential impulse response and comparing them tothe corresponding reference values.

By configuring vocal tract 104 into certain geometric shapes, operator102 can cause HM interface 110 to generate distinguishable signals thatcan be analyzed in terms of their features and mapped onto a set ofcommands/instructions. For example, while operating in a training mode,HM interface 110 can collect user-specific reference data and create a“map” of signal features according to which the detected impulseresponses can be translated into the correspondingcommand(s)/instruction(s). The map is stored in the memory of HMinterface 110 and invoked during normal operation of system 100. Basedon the map, HM interface 110 interprets real-time vocal-tractreflectometry data and generates the corresponding appropriate controlsignal 138 for controller 140. Representative training procedures thatcan be used to collect user-specific reference data for HM interface 110are disclosed, e.g., in the above-referenced U.S. Patent ApplicationPublication No. 2010/0131268.

As already indicated above, the use of both analog and digitalcommands/instructions is possible. A representative example ofgenerating an analog command is operator 102 moving the tip of thetongue from the upper-left wisdom tooth to the upper-right wisdom toothwhile HM interface 110 is tracking the tongue position and translatingthe tongue displacement with respect to a reference position into ananalog value. Controller 140 can then use this analog value to changesome continuously variable operating parameter, such as the brightnessof the image in night goggles 150 or the speed of vehicle 150. In oneconfiguration, HM interface 110 enables operator 102 to use his/hertongue as a two-dimensional analog joystick, with an up/down tonguemotion corresponding to one degree of freedom of the joystick and aleft/right tongue motion corresponding to another degree of freedom.

The spatial resolution with which HM interface 110 can distinguishdifferent geometric shapes of vocal tract 104 depends on the number ofmicrophones 118 and their frequency characteristics, the characteristicfrequencies and bandwidth of the excitation signal applied to the vocaltract by speaker 116, and the bandwidth of the recorded signal. Anypossible command ambiguities due to the imprecise control of thegeometric shape of vocal tract 104 by operator 102 and/or inadequatespatial resolution achieved by HM interface 110 can be resolved, e.g.,by providing some form of feedback to the operator. In one embodiment,HM interface 110 is configured to provide an audio-feedback signal tooperator 102 via an earpiece 132. Various visual forms of feedback arealso contemplated, e.g., using a display screen 134. Based on thefeedback signal(s), operator 102 can make a vocal-tract adjustment toenable HM interface 110 to unambiguously interpret the correspondingimpulse-response features.

FIGS. 2A-2B show front and back views, respectively, of a sensorassembly 200 that can be used in HM interface 110 (FIG. 1) according toone embodiment of the invention. More specifically, when operator 102wears sensor assembly 200, the front view shown in FIG. 2A correspondsto the frontal full-face view. The back view shown in FIG. 2Bcorresponds to a view from the interior of the operator's mouth.

Sensor assembly 200 comprises a mouthpiece 210 that can be similar inshape to a conventional mouthguard, e.g., a protective device for themouth that covers the teeth and sometimes gums to prevent or reduceinjury in contact sports or as part of certain dental procedures, suchas tooth bleaching. Mouthpiece 210 is horseshoe-shaped and has an uppergroove 212 a and a lower groove 212 b configured to accommodate theupper and lower arches of teeth, respectively. In various embodiments,mouthpiece 210 can be manufactured to have a relatively looselyaccommodating shape that can fit the mouths of most operators or,alternatively, can be custom-molded to fit very closely to the teeth andgums of the particular operator 102. When worn by operator 102,mouthpiece 210 locks the operator's mandible and maxilla with respect toone another, which eliminates some degrees of freedom in vocal tract104. The latter can be beneficial, e.g., for improving signalreproducibility and simplifying the concomitant signal processingimplemented in processor 124.

In a representative embodiment, mouthpiece 210 has an approximatelysymmetric U shape characterized by two planes of approximate symmetry,both of which planes are orthogonal to the plane of FIG. 2. A firstapproximate-symmetry plane 202 is orthogonal to the plane of the U. Asecond approximate-symmetry plane 204 is parallel to the plane of the U.

Sensor assembly 200 further comprises a speaker 216 and sevenmicrophones 218 ₁-218 ₇, all of which are imbedded into a lingual wall214 of mouthpiece 210 as indicated in FIG. 2B. A plurality of electricallead wires 220 for electrically and respectively connecting speaker 216and microphones 218 ₁-218 ₇ to D/A converter 114 and A/D converter 122(FIG. 1) protrude out from a labial wall 224 of mouthpiece 210 asindicated in FIG. 2A. In one embodiment, electrical lead wires 220 canbe arranged into a cable (not explicitly shown in FIG. 2A). In analternative embodiment, mouthpiece 210 incorporates a power source(e.g., a battery) and a short-range wireless transceiver (e.g., aBluetooth transceiver), which eliminate the need for electrical leadwires 220. In this case, the base unit of HM interface 110 includes acorresponding short-range wireless transceiver configured to communicatewith the wireless transceiver in mouthpiece 210.

In one embodiment, speaker 216 and microphone 218 ₄ are positioned toapproximately line up with approximate-symmetry plane 202. Speaker 216and microphones 218 ₂ and 218 ₆ are positioned to approximately line upwith approximate-symmetry plane 204. Microphones 218 ₁-218 ₃ arepositioned to the left of plane 202, and microphones 218 ₅-218 ₇ arepositioned to the right of plane 202. Microphones 218 ₃-218 ₅ arepositioned above plane 204, and microphones 218 ₁ and 218 ₇ arepositioned below plane 204. The arrangement of microphones 218 ₁-218 ₇does not have to be symmetric, although certain benefits may accrue froma symmetric placement of the microphones. Taken together, microphones218 ₁-218 ₇ form a phase-arrayed acoustic detector that advantageouslyenables HM interface 110 to sense both lateral (left/right and up/down)and longitudinal (forward/backward) movements of the tongue. In analternative embodiment, a different number of microphones 218 cansimilarly be used.

FIG. 3 shows a perspective three-dimensional view of a sensor assembly300 that can be used in HM interface 110 (FIG. 1) according to anotherembodiment of the invention. Also shown in FIG. 3 is the lower arch 302of teeth in the mouth of operator 102, to which sensor assembly 300 isform-fitted. The vertical dashed lines with arrows indicate how sensorassembly 300 is placed over arch 302.

Sensor assembly 300 comprises a U-shaped dental brace 310 configured fora relatively tight (e.g., form-fitting or snap-on) fit onto the teeth ofarch 302. Sensor assembly 300 further comprises a speaker 316 and threeMEMS microphones 318 ₁-318 ₃ that are attached to brace 310 as indicatedin FIG. 3. Note that the view of microphone 318 ₃ is somewhat obscuredby the corresponding side of brace 310. However, the way in whichmicrophone 318 ₃ is attached to brace 310 can be inferred from that ofmicrophone 318 ₁, which is similarly attached at the other(non-obscured) side of the brace. Electrical lead wires 320 run alongthe lingual surface of brace 310 from an entry point 326 to microphone318 ₁. Similar electrical lead wires (not clearly visible in FIG. 3) runfrom entry point 326 to speaker 316 and each of microphones 318 ₁-318 ₂.At the labial side of brace 310, these electrical wires are assembledinto a cable 322.

While the use of condenser microphones instead of MEMS microphones 318is possible in alternative embodiments of sensor assembly 300, the useof MEMS microphones provides the benefit of a smaller size and lowerpower consumption. Each of microphones 318 has a housing that seals themicrophone against saliva and other fluids to enable long-term wearingand even some food consumption with sensor assembly 300 remaining in theoperator's mouth. Similar to sensor assembly 200, sensor assembly 300can be modified for wireless operation. In an alternative embodiment,brace 310 can be configured to fit an upper arch of teeth and/or have adifferent number of microphones 318.

FIG. 4 shows a perspective three-dimensional view of a sensor assembly400 that can be used in HM interface 110 (FIG. 1) according to yetanother embodiment of the invention. Sensor assembly 400 differs fromeach of sensor assemblies 200 (FIG. 2) and 300 (FIG. 3) in that sensorassembly 400 has a speaker 416 and a microphone 418 that can optionallybe positioned outside the mouth of operator 102, e.g., for tracking theposition and/or movement of the operator's lips.

Sensor assembly 400 comprises a U-shaped dental brace 410 configured fora relatively tight fit to the upper or lower arch of teeth, such as arch302 (FIG. 3), in the mouth of operator 102. In one embodiment, the wholesensor assembly 300 (including dental brace 310, speaker 316,microphones 318 ₁-318 ₃, wires 320, and cable 322) can be used toimplement dental brace 410.

Speaker 416 and microphone 418 are attached to brace 410 using aC-shaped holder 428. In one embodiment, holder 428 has a horizontalextension rod (not visible in FIG. 4) at the proximal end of the C. Theextension rod fits between the lips and positions the proximal end ofthe C just outside the mouth. The distal end of the C (labeled 426 inFIG. 4) is attached to a handle 424 that is connected to the backside ofspeaker 416. Operator 102 can use handle 424, e.g., to hold sensorassembly 400 when brace 410 is being inserted into and secured insidethe mouth. An electrical cable 422 for providing electrical connectionsto speaker 416 and microphone 418 is fitted through handle 424 asindicated in FIG. 4. Depending on the length of holder 428 and the pointof attachment of distal end 426 to handle 424, speaker 416 andmicrophone 418 can be placed (1) outside of the operator's mouth, (2)inside the operator's mouth, or (3) between the operator's lips. In thesecond and third configurations, operator 102 needs to keep his/hermouth slightly open to enable sensor assembly 400 to probe vocal tract102. In the first configuration, the mouth can be closed, and speaker416 and microphone 418 can be used for tracking the lips. Similar to thetongue movements that can be detected using sensor assemblies 200 and300 (see FIGS. 2-3), lip movements detected using sensor assembly 400can be used to generate control signal 138 for controller 140 (FIG. 1).

In one embodiment, microphone 418 and speaker 416 are mounted in anaxially symmetric configuration, with the microphone placed in front ofthe speaker using a crossbeam 420 whose ends are attached to the outerrim of the speaker as indicated in FIG. 4. The diameter of microphone418 is smaller than the diameter of the active area of speaker 416,which enables the acoustic waves generated by the speaker to go aroundthe microphone toward the mouth and/or vocal tract of operator 102. Thereflected acoustic waves are detected by microphone 418, and theresulting electrical signals are directed, via cable 422, to processor124 (FIG. 1) for processing and analysis.

In an alternative embodiment, the diameter of microphone 418 does nothave to be smaller than the diameter of the active area of speaker 416and/or a different placement geometry of the microphone and speaker withrespect to one another (e.g., side by side) can similarly be used.

FIGS. 5A-5B show perspective three-dimensional views of a headset 500that can be used in HM interface 110 (FIG. 1) according to yet anotherembodiment of the invention. More specifically, FIG. 5A shows an overallview of headset 500. FIG. 5B shows an enlarged view of a circuit 544located in a sensor assembly 540 of headset 500.

Referring to FIG. 5A, headset comprises a headband 510 with a temple pad508 attached at one end and an earcup 532 attached at the other end.Connected to earcup 532 is a boom arm 514 having sensor assembly 540 atits distal end. A ball joint 512 located between earcup 532 and boom arm514 enables two degrees of freedom for rotating the boom arm withrespect to the earcup. More specifically, a first degree of freedomcorresponds to a rotation that moves the distal end of boom arm 514approximately up or down. A second degree of freedom corresponds to arotation that moves the distal end of boom arm 514 in (toward the lips)or out (away from the lips) in the horizontal plane. In one embodiment,earcup 532 and a speaker housed therein (not explicitly shown in FIG.5A) implement earpiece 132 (FIG. 1). A cable 522 provides appropriateelectrical connections for the circuitry housed in ear cup 532 and insensor assembly 540.

Referring to FIG. 5B, circuit 544 includes a speaker 516, a MEMSmicrophone 518, and a miniature video camera 520, all mounted on acircuit board 542. An extension 524 of cable 522 provides electricalconnections for circuit board 542 and the various circuit elementsconnected thereto. Speaker 516 and microphone 518 can be used to trackthe motion of the lips of operator 102, e.g., as already described abovein reference to FIG. 4. Images captured by video camera 520 can be usedby HM interface 110 to determine the position of sensor assembly 540with respect to certain reference points, such as the maxillary anteriorteeth in the mouth of operator 102. The determined sensor position istaken into account by processor 124 to make appropriate adjustments inthe analysis of the acoustic echo signals detected by microphone 518.

In one embodiment, video camera 520 is a CameraCube manufactured byOmniVision Technologies, Inc., of Santa Clara, Calif.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense.

In various embodiments, HM interface 110 may have more than onebiometric-sensor assembly. For example, headset 500 (FIG. 5) can be usedtogether with sensor assembly 200 (FIG. 2) or sensor assembly 300 (FIG.3).

Although sensor assemblies 200, 300, 400, and 540 (FIGS. 2-5) have beendescribed in reference to HM interface 110, the use of said sensorassemblies is not so limited. Various embodiments of sensor assemblies200, 300, 400, and 540 can similarly be used in other suitable systems.One representative example of such other system is a voice-estimationinterface disclosed in the above-cited U.S. Patent ApplicationPublication No. 2010/0131268. Another representative example is the useof sensor assembly 540 (FIG. 5) for lip-reading.

For the purposes of this specification and claims, the variousarticulators of vocal tract 104, such as the velum, tongue, lips, andjaws, are considered to be parts of the vocal tract.

In various embodiments, variously shaped dental appliances known in thedental arts can be adapted to implement mouthpieces (e.g., analogous tomouthpiece 210, FIG. 2) and/or dental braces (e.g., analogous to braces310 and 410, FIGS. 3-4) without departing from the scope and principleof the invention(s).

Various wireless arrangements, such as inductively coupled loops, can beused to power circuits located in the mouth of operator 102.

As used in the claims, the term “machine” should be construed to cover,for example, any of (i) a device or system comprising fixed and/ormoving parts that modifies or transfers energy and/or generatesmechanical movement, (ii) an electronic device or system, e.g., acomputer, a radio, a telephone, or a consumer appliance, (iii) anoptical device or system, (iv) an acoustic device or system, (v) avehicle, (vi) a weapon, (vii) a piece of equipment that performs orassists in the performance of a human task, and (viii) a semi or fullyautomated device that magnifies human physical and/or mentalcapabilities in performing one or more operations.

Various modifications of the described embodiments, as well as otherembodiments of the invention, which are apparent to persons skilled inthe art to which the invention pertains are deemed to lie within theprinciple and scope of the invention as expressed in the followingclaims.

Unless explicitly stated otherwise, each numerical value and rangeshould be interpreted as being approximate as if the word “about” or“approximately” preceded the value of the value or range.

It will be further understood that various changes in the details,materials, and arrangements of the parts which have been described andillustrated in order to explain the nature of this invention may be madeby those skilled in the art without departing from the scope of theinvention as expressed in the following claims.

The use of figure numbers and/or figure reference labels in the claimsis intended to identify one or more possible embodiments of the claimedsubject matter in order to facilitate the interpretation of the claims.Such use is not to be construed as necessarily limiting the scope ofthose claims to the embodiments shown in the corresponding figures.

Although the elements in the following method claims, if any, arerecited in a particular sequence with corresponding labeling, unless theclaim recitations otherwise imply a particular sequence for implementingsome or all of those elements, those elements are not necessarilyintended to be limited to being implemented in that particular sequence.

Reference herein to “one embodiment” or “an embodiment” means that aparticular feature, structure, or characteristic described in connectionwith the embodiment can be included in at least one embodiment of theinvention. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment, nor are separate or alternative embodiments necessarilymutually exclusive of other embodiments. The same applies to the term“implementation.”

Also for purposes of this description, the terms “couple,” “coupling,”“coupled,” “connect,” “connecting,” or “connected” refer to any mannerknown in the art or later developed in which energy is allowed to betransferred between two or more elements, and the interposition of oneor more additional elements is contemplated, although not required.Conversely, the terms “directly coupled,” “directly connected,” etc.,imply the absence of such additional elements.

The description and drawings merely illustrate the principles of theinvention. It will thus be appreciated that those of ordinary skill inthe art will be able to devise various arrangements that, although notexplicitly described or shown herein, embody the principles of theinvention and are included within its spirit and scope. Furthermore, allexamples recited herein are principally intended expressly to be onlyfor pedagogical purposes to aid the reader in understanding theprinciples of the invention and the concepts contributed by theinventor(s) to furthering the art, and are to be construed as beingwithout limitation to such specifically recited examples and conditions.Moreover, all statements herein reciting principles, aspects, andembodiments of the invention, as well as specific examples thereof, areintended to encompass equivalents thereof.

The functions of the various elements shown in the figures, includingany functional blocks labeled as “processors,” may be provided throughthe use of dedicated hardware as well as hardware capable of executingsoftware in association with appropriate software. When provided by aprocessor, the functions may be provided by a single dedicatedprocessor, by a single shared processor, or by a plurality of individualprocessors, some of which may be shared. Moreover, explicit use of theterm “processor” or “controller” should not be construed to referexclusively to hardware capable of executing software, and mayimplicitly include, without limitation, digital signal processor (DSP)hardware, network processor, application specific integrated circuit(ASIC), field programmable gate array (FPGA), read only memory (ROM) forstoring software, random access memory (RAM), and non volatile storage.Other hardware, conventional and/or custom, may also be included.Similarly, any switches shown in the figures are conceptual only. Theirfunction may be carried out through the operation of program logic,through dedicated logic, through the interaction of program control anddedicated logic, or even manually, the particular technique beingselectable by the implementer as more specifically understood from thecontext.

1. An apparatus, comprising: a first acoustic speaker; a first set ofone or more acoustic microphones; and a dental appliance, wherein: thefirst acoustic speaker and the first set of one or more acousticmicrophones are attached to the dental appliance so that, when thedental appliance is placed into a user's mouth: the first acousticspeaker has a position that causes acoustic waves generated by the firstacoustic speaker to enter the user's vocal tract; and the first set ofone or more acoustic microphones has a position that causes acousticwaves reflected from the vocal tract to impinge onto at least onemicrophone of the first set.
 2. The apparatus of claim 1, wherein thedental appliance comprises a mouthpiece having a first groove and asecond groove located on opposite sides of the mouthpiece and configuredto accommodate an upper arch of teeth and a lower arch of teeth,respectively, when inserted into the mouth.
 3. The apparatus of claim 2,wherein the first and second grooves are configured to lock the user'smandible and maxilla with respect to one another.
 4. The apparatus ofclaim 2, wherein: the first acoustic speaker is imbedded into a lingualwall of the mouthpiece; and the first set of one or more acousticmicrophones is imbedded into the lingual wall.
 5. The apparatus of claim2, further comprising a set of electrical wires configured to provideelectrical connections to the first acoustic speaker and/or the firstset of one or more acoustic microphones, wherein the electrical wiresprotrude out from a labial wall of the mouthpiece.
 6. The apparatus ofclaim 2, wherein: the mouthpiece has a U shape characterized by anapproximate-symmetry plane; at least one microphone of the first set islocated to one side of the approximate-symmetry plane; and at least oneother microphone of the first set is located to another side of theapproximate-symmetry plane.
 7. The apparatus of claim 1, wherein: thedental appliance comprises a dental brace shaped to form-fit a specifiedarch of teeth; the first acoustic speaker is attached to the dentalbrace; and the first set of one or more acoustic microphones is attachedto the dental brace.
 8. The apparatus of claim 7, wherein the specifiedarch is a lower arch.
 9. The apparatus of claim 7, wherein the firstacoustic speaker is attached to the dental brace so that, when thedental brace is placed in the mouth, the first acoustic speaker islocated inside the mouth.
 10. The apparatus of claim 7, wherein thefirst set of one or more acoustic microphones is attached to the dentalbrace so that, when the dental brace is placed in the mouth, the firstset of one or more acoustic microphones is located inside the mouth. 11.The apparatus of claim 7, wherein the first acoustic speaker is attachedto the dental brace so that, when the dental brace is placed in themouth, the first acoustic speaker is located between the user's lips.12. The apparatus of claim 7, further comprising a second acousticspeaker attached to the dental brace so that, when the dental brace isplaced in the mouth, the second acoustic speaker is located outside themouth.
 13. The apparatus of claim 7, further comprising a second set ofone or more acoustic microphones attached to the dental brace so that,when the dental brace is placed in the mouth, the second set of one ormore acoustic microphones is located outside the mouth.
 14. Theapparatus of claim 1, further comprising: a second acoustic speaker; asecond set of one or more acoustic microphones; and a headset having anearpiece and a boom arm that is movable with respect to the earpiece,wherein both the second acoustic speaker and the second set of one ormore acoustic microphones are mounted on the boom arm.
 15. The apparatusof claim 14, further comprising a video camera mounted on the boom arm.16. The apparatus of claim 14, wherein: the second acoustic speaker isconfigured to generate second acoustic waves; and when the headset isplaced onto the user's head: the second acoustic speaker has a positionthat causes the second acoustic waves to reflect off the user's lips;and the second set of one or more acoustic microphones has a positionthat causes said reflected second acoustic waves to impinge onto atleast one acoustic microphone of the second set.
 17. The apparatus ofclaim 1, further comprising a power source configured to provideelectrical power to the first acoustic speaker and/or the first set ofone or more acoustic microphones, wherein the power source isincorporated into or attached to the dental appliance.
 18. The apparatusof claim 1, further comprising a wireless transceiver configured to:receive control signals for the first acoustic speaker from an externaltransmitter; and/or transmit signals generated by the first set of oneor more acoustic microphones to an external receiver, wherein thewireless transmitter is incorporated into or attached to the dentalappliance.
 19. An apparatus, comprising: an acoustic speaker; a set ofone or more acoustic microphones; and a headset having an earpiece and aboom arm that is movable with respect to the earpiece, wherein: theacoustic speaker is mounted on the boom arm; and the set of one or moreacoustic microphones is mounted on the boom arm.
 20. The apparatus ofclaim 19, further comprising a video camera mounted on the boom arm.